Raycasting around a gameObject while it's rotating

Questions & Answers
1

Hello, I have a gameObject that is a rectangle and im raycasting around it to check if it hits something. It works great when the object has 0 rotation. As soon as the rotation changes then the raycasts dont work because the math involed to calculate the raycasting spots are wrong. I was wondering if there is a way to rotate the gameObject after the raycasts have been set, so I can get the effect that I want.

The gameObject is inside a Canvas so im working in 2D screen space.

Any help would be much appreciated!

The code in C# that I use:

public bool RaycastCheck()
    {
        var size =
            new Vector2(_collider.size.x * Mathf.Abs(transform.localScale.x),
                _collider.size.y * Mathf.Abs(transform.localScale.y)) / 2;

        var center = new Vector2(_collider.center.x * transform.localScale.x, _collider.center.y * transform.localScale.y);

        Vector3 _raycastTopLeft = transform.position + new Vector3(center.x - size.x, center.y + size.y);
        Vector3 _raycastBottomRight = transform.position + new Vector3(center.x + size.x, center.y - size.y);
        Vector3 _raycastBottomLeft = transform.position + new Vector3(center.x - size.x, center.y - size.y);

        Debug.Log("topleft"+_raycastTopLeft);
        Debug.Log("bottomleft" + _raycastBottomLeft);
        Debug.Log("bottomeright" + _raycastBottomRight);

        float verticalDistaceBetweenRays = (_collider.size.x * Mathf.Abs(transform.localScale.x)) / 9;
        float horizontalDistanceBetweenRays = (_collider.size.y * Mathf.Abs(transform.localScale.y)) / 3;

        Vector2 transformUp = GetComponent<RectTransform>().rotation * Vector2.up;
        Vector2 transformDown = GetComponent<RectTransform>().rotation * -Vector2.up;
        Vector2 transformRight = GetComponent<RectTransform>().rotation * Vector2.right;
        Vector2 transformLeft = GetComponent<RectTransform>().rotation * -Vector2.right;


        for (int i = 0; i < 10; i++)
        {
            var rayVector = new Vector2(_raycastTopLeft.x + (i * verticalDistaceBetweenRays), _raycastTopLeft.y);
            var rayVector1 = new Vector2(_raycastBottomLeft.x + (i * verticalDistaceBetweenRays), _raycastBottomLeft.y);

            Debug.DrawRay(rayVector, transformUp * 3.5f, Color.red);
            Debug.DrawRay(rayVector1, transformDown * 3.5f, Color.red);

            var rayCastHit = Physics2D.Raycast(rayVector, transformUp, 3.5f);
            var rayCastHit1 = Physics2D.Raycast(rayVector1, transformDown, 3.5f);
            if (rayCastHit || rayCastHit1)
            {
                //Debug.Log("HIT");
                return false;
            }
        }

        for (int i = 0; i < 4; i++)
        {
            var rayVector = new Vector2(_raycastBottomLeft.x, _raycastBottomLeft.y + (i * horizontalDistanceBetweenRays));
            var rayVector1 = new Vector2(_raycastBottomRight.x, _raycastBottomRight.y + (i * horizontalDistanceBetweenRays));

            Debug.DrawRay(rayVector, transformLeft * 3.5f, Color.red);
            Debug.DrawRay(rayVector1, transformRight * 3.5f, Color.red);

            var rayCastHit = Physics2D.Raycast(rayVector, transformLeft, 3.5f);
            var rayCastHit1 = Physics2D.Raycast(rayVector1, transformRight, 3.5f);
            if ((rayCastHit.collider != null) || (rayCastHit1.collider != null))
            {
                //Debug.Log("HIT");
                return false;
            }
        }
        return true;
    }

Here is a visualization of what I want:

33741-unityhelp.jpg
33741-unityhelp.jpg1000×562 35.2 KB

2

My usual solution for this problem is to use local coordinates. So for each ray, you would specify a local position and a local direction. The local forward of an object is always Vector3.forward. The center of the object is always Vector3.zero. Local coordinates are always calculated based on a local scale of (1,1,1). The front, left, top corner of a cube has a local coordinate of (-.5, .5, .5) regardless of the size, position, or rotation of the cube.

For the number of raycasts you are doing, consider using an array.

Then when you do the Raycast(), you can do:

  var rayCastHit = Physics2D.Raycast(transform.TransformPoint(localPosition), transform.TransformDirection(localDirection), 3.5f);

The Transform.TransformPoint() call and Transform.TransformDirection() call take the local position and direction and transforms them into world space…it takes into account changes in position, rotation and scale.